Search PubMed⌕ Search

PubMed · 8718332

Experimental designs.

Abstract

This article discusses randomized clinical trials, double blind designs and factorial designs and describes and explains their main requirements. It is shown that the randomized clinical trial is not a different experimental design, but is one that reflects the purpose for and the scale on which the post-test only or pre-test/post-test designs are often used. A common method for the prevention of experimenter bias in clinical trials is the double blind trial. Factorial designs make the simultaneous manipulation of two or more independent variables possible, thus producing data about their effect on the development variable.

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

R Behi, M Nolan. Experimental designs.. https://doi.org/10.12968/bjon.1996.5.12.754

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

Blinding in randomised trials: hiding who got what.

Blinding embodies a rich history spanning over two centuries. Most researchers worldwide understand blinding terminology, but confusion lurks beyond a general comprehension. Terms such as single blind, double blind, and triple blind mean different things to different people. Moreover, many medical researchers confuse blinding with allocation concealment. Such confusion indicates misunderstandings of both. The term blinding refers to keeping trial participants, investigators (usually health-care providers), or assessors (those collecting outcome data) unaware of the assigned intervention, so that they will not be influenced by that knowledge. Blinding usually reduces differential assessment of outcomes (information bias), but can also improve compliance and retention of trial participants while reducing biased supplemental care or treatment (sometimes called co-intervention). Many investigators and readers naïvely consider a randomised trial as high quality simply because it is double blind, as if double-blinding is the sine qua non of a randomised controlled trial. Although double blinding (blinding investigators, participants, and outcome assessors) indicates a strong design, trials that are not double blinded should not automatically be deemed inferior. Rather than solely relying on terminology like double blinding, researchers should explicitly state who was blinded, and how. We recommend placing greater credence in results when investigators at least blind outcome assessments, except with objective outcomes, such as death, which leave little room for bias. If investigators properly report their blinding efforts, readers can judge them. Unfortunately, many articles do not contain proper reporting. If an article claims blinding without any accompanying clarification, readers should remain sceptical about its effect on bias reduction.

Double-Blind Method↗

[Double-blind peer review].

The peer review process in medical sciences is much debated. The method is not yet evidence based. Who are the reviewers and how do they perform? They are "independent" experts. As such they are bound to be involved in research similar to that outlined in the manuscript. Very often they are contestant in the same race. That is why the author consider the double blind method, where the author is blinded and the reviewer masked from each other's identity, the best choice. Nevertheless in very many scientific journals of high quality and envied impact factors do not blind the identity of the authors. Science is a race for fame, self accomplishment and also a means to get grants for pursuing the scientific research. Only success is able to provide resources for expensive scientific research. There is no fail-safe method against bias in grant giving and editorial process. In the tidal wave of electronic information it is mandatory to help in differentiating between signal and noise in science. Peer review is the best method to protect readers from the trash of uncontrolled publications in medical science.

Double-Blind Method↗